The number of pedestrians killed by motor vehicles on U.S. roads remains at or near levels not seen in more than a quarter of a century.

A new report released Wednesday calculates that 5984 pedestrians were killed in motor-vehicle crashes in 2017, according to preliminary data. If those numbers hold, they’re essentially unchanged from the 5987 deaths documented one year earlier. Both are the highest numbers recorded since 6482 were killed in 1990, according to federal data.

The deadly figures are the continuation of a decade-long trend, according to the Governors Highway Safety Association (GHSA), which published the report. Over the past decade for which final numbers are available, the number of pedestrian fatalities increased 27 percent. All other traffic deaths fell by 14 percent in the same timeframe, though the overall numbers have been on their own steep climb over the past five years, reaching 37,461 deaths in 2016.

Those divergent trends highlight safety gains made by automakers, whose vehicles face more rigorous crash-test scrutiny and are now equipped with more active and passive safety systems, like collision-avoidance warnings. And they highlight the hostile road conditions that vulnerable road users are increasingly facing.

“Two consecutive years of 6000 pedestrian deaths is a red flag for all of us in the traffic safety community,” said Jonathan Adkins, GHSA executive director. “These levels are no longer a blip, but unfortunately a sustained trend. We can’t afford to let this be the new normal.”

Pedestrians now account for 16 percent of all traffic deaths, the largest proportion in 33 years. Transportation officials both in the government and in safety organizations have been scrambling to address the decade-long rise, and in some respects, the plateau between the 2016 and 2017 numbers suggests their efforts may have thwarted further increases.

But the source of the scourge remains nebulous—everything from more driving because of improving economic conditions to lower fuel prices and warmer weather patterns may have contributed to the numbers. The GHSA report raises the questions—but does not definitively answer—whether the legalization of marijuana in some states and the rise in smartphone use may be culprits.

“Without making a direct correlation or claiming a definitive link, more recent factors contributing to the increase in pedestrian fatalities might include the growing number of state and local governments that have decriminalized the recreational use of marijuana, which can impair judgment and reaction time for all road users,” the report said.

Several states where marijuana use has become legal collectively logged a 16.4 percent increase in pedestrian deaths during the first six months of 2017 compared to the first six months of 2016. (The states named in the study were Alaska, Colorado, Maine, Massachusetts, Nevada, Oregon, and Washington, plus the District of Columbia.) All other states reported a collective 5.8 percent decrease during the same period.

The national average is 1.9 pedestrian deaths per 100,000 residents. But the number of states with a fatality rate at or above 2.0 per 100,000 residents has more than doubled, from seven in 2014 to 15 in 2016. In the nation’s 10 largest cities, the GHSA report found a 28 percent increase in fatalities, even though more cities are adopting Vision Zero goals of eradicating traffic deaths through redesigned infrastructure and more aggressive enforcement.

Los Angeles County holds special distinction as being the most deadly county for pedestrians: 265 were killed there in 2016, the latest year for which county-specific numbers were available. That’s nearly double the second highest: Maricopa County, Arizona, which contains Phoenix and its suburbs, had 133 pedestrian deaths in 2016.

The latest figures were discouraging to safety organizations that have tracked the increase closely and lobbied for a more aggressive response from federal safety regulators. “When it comes to deaths on our roads, our nation seems content to simply tread water,” said Deborah A.P. Hersman, president and CEO of the National Safety Council. “We are apathetic to the issue, and this complacency is killing us.”